Field of the Invention
The present invention relates to a cleaning liquid for lithography. More specifically, the invention relates to a cleaning liquid for lithography that can effectively clean and remove residue materials remaining after etching without corroding corrosion-prone materials such as low dielectric constant materials.
The present invention further relates to a method for forming a wiring using the cleaning liquid for lithography.
Related Art
A semiconductor device laminates a metallic wiring layer, a low dielectric constant layer, an insulation layer, or the like on a substrate such as a silicon wafer, and the like. This type of semiconductor device is manufactured by processing each layer using a lithography method that employs an etching process using a resist pattern as a mask.
The resist film or a temporary laminate film (termed “a sacrificial film”) used in the lithography method, and furthermore residue material produced during the etching process is removed using a cleaning liquid to prevent an adverse effect on the semiconductor device, and furthermore to prevent impediment to a subsequent processing step.
In recent years, methods for forming a wiring using a damascene method have been employed in respond to advances in high-density and highly integrated semiconductor devices. Copper that is prone to undergo corrosion is used as a metallic wiring material that configures the metallic wiring layer of the semiconductor device in this type of wiring formation method. Furthermore, a low dielectric constant material (termed an “Low-k material”) is used to configure the low dielectric constant layer. Advances in achieving a low dielectric constant have resulted in use of such Low-k materials that are prone to undergo corrosion. Consequently, there is a need for development of a cleaning liquid that does not cause corrosion of such corrosion-prone materials when cleaning the substrate.
In particular, a Low-k material having a dielectric constant (k) of 2.5 or less, which is called an ultra-Low-k (ULK) material, is very easily damaged by an alkali or an acid used as a cleaning liquid and tends to thereby readily cause changes in size, k value, contact angle, etc. Such damage occurs not only in the cleaning step with a cleaning liquid but also in steps of CMP, etching, and ashing. As the ULK material, for example, a porous SiO2 film is used.
Conventionally, in order to inhibit damage of ULK materials, cleaning is performed using a weak alkaline cleaning liquid having a lowered pH. This can certainly inhibit damage of ULK materials, but reduces the ability of removing residue materials.
In order to reduce the damage during cleaning of a ULK material, a method for treating the damaged surface of the ULK material by etching with a supercritical silylating agent and a supercritical solvent has been proposed (Patent Literature 1). This method can at least partially passivate the surface of a ULK material. Therefore, even if the etched ULK material is treated with a cleaning liquid, the damage of the ULK material can be suppressed to a minimum.
[Patent Document 1] Japanese Unexamined Patent Application, Publication No. 2005-522737